ESPRESSIF SYSTEMS PTE LTD ESP32SOLO1C Manuel D’Utilisation
CONFIDENTIAL
2. Pin Definitions
• MTDI
• GPIO0
• GPIO2
• MTDO
• GPIO5
Software can read the values of these five bits from register ”GPIO_STRAPPING”.
During the chip’s system reset (power-on-reset, RTC watchdog reset and brownout reset), the latches of the
strapping pins sample the voltage level as strapping bits of ”0” or ”1”, and hold these bits until the chip is
powered down or shut down. The strapping bits configure the device’s boot mode, the operating voltage of
VDD_SDIO and other initial system settings.
Each strapping pin is connected to its internal pull-up/pull-down during the chip reset. Consequently, if a
strapping pin is unconnected or the connected external circuit is high-impedance, the internal weak
pull-up/pull-down will determine the default input level of the strapping pins.
To change the strapping bit values, users can apply the external pull-down/pull-up resistances, or use the host
MCU’s GPIOs to control the voltage level of these pins when powering on ESP32.
After reset, the strapping pins work as normal-function pins.
Refer to Table
for a detailed boot-mode configuration by strapping pins.
Table 3: Strapping Pins
Voltage of Internal LDO (VDD_SDIO)
Pin
Default
3.3 V
1.8 V
MTDI
Pull-down
0
1
Booting Mode
Pin
Default
SPI Boot
Download Boot
GPIO0
Pull-up
1
0
GPIO2
Pull-down
Don’t-care
0
Enabling/Disabling Debugging Log Print over U0TXD During Booting
Pin
Default
U0TXD Active
U0TXD Silent
MTDO
Pull-up
1
0
Timing of SDIO Slave
Pin
Default
Falling-edge
Input
Falling-edge Output
Falling-edge
Input
Rising-edge Output
Rising-edge
Input
Falling-edge Output
Rising-edge
Input
Rising-edge Output
MTDO
Pull-up
0
0
1
1
GPIO5
Pull-up
0
1
0
1
Note:
• Firmware can configure register bits to change the settings of ”Voltage of Internal LDO (VDD_SDIO)” and ”Timing
of SDIO Slave” after booting.
• The module integrates a 3.3 V SPI flash, so the pin MTDI cannot be set to 1 when the module is powered up.
Espressif Systems
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ESP32-SOLO-1C Datasheet V0.1